This invention relates to the identification of cells suitable for transplantation into a vertebrate brain. More particularly, this invention relates to the identification of multipotent neural cells which are able to repair neural damage following transplantation into the brain.
There is an increasing awareness that damage to a vertebrate brain can be repaired using cell transplantation technology. Typically, the cell transplanted into a damaged brain will be a neural stem cell, e.g. a pluripotent neuroepithelial stem cell which is capable of differentiating into a cell with a neural cell phenotype.
For example, Sinden et al., Neuroscience (1997) 81:599-608 , discloses that conditionally-immortalised hippocampus neuroepithelial stem cells can be used to improve spatial learning after transplantation into the ischaernia-leisoned hippocampus. See also WO-A-97/10329.
However, it has been found that not all neural stem cells can be transplanted for successful repair of neural damage.
For example, while MHP36 cells (Sinden et al., supra) do aid repair, an apparently similar cell line, MHP15, fails to repair. This difference emerges despite the fact that both MHP cell lines were generated from the same tissue source (namely hippocampus), and both are multipotent neural precursor cell lines, i.e. both cell lines have the capacity to generate a full complement of brain cell types, including neurons, astrocytes and oligodendrocytes.
Therefore, it would be beneficial if it were possible to identify at an early state, the cells that were suitable for transplantation, or to have the ability to modify cell lines in order to achieve successful transplantation and repair.
The present invention is based on the realisation that cells that are suitable for transplantation and repair may be identified on the basis of their gene expression profile.
The present invention employs, for example, a technique termed differential display (DD) to investigate the differences between repairing and non-repairing cell lines. Differential display is used to visualise the differences in gene expression between two or more cell lines, and it has been found that cell lines that repair have very similar profiles of gene expression but very different profiles from those cells that do not repair. This represents a major, unexpected discovery because, apart from their capacity to repair, the cell lines are usually remarkably similar, in morphology, growth characteristics and growth factor responsivity.
According to one aspect of the present invention, a method for selecting a cell suitable for transplantation into a damaged vertebrate brain comprises:
(i) isolating cells that are, or are capable of differentiating into, a cell with a neural cell phenotype;
(ii) obtaining the gene expression profile of the cells;
(iii) comparing the expression profile of the cells with that from a control cell known to be suitable for transplantation; and
(iv) selecting those cells with a similar expression profile to that of the control.
In one embodiment of the invention, the control cell is from the MHP 36 cell line. Step (ii) may be carried out by differential display.
The present invention is not only useful for identifying suitable cells for transplantation, but may be used to identify genes or gene products that may be involved in determining whether or not a neural cell can repair, or not.
According to a further aspect of the present invention, a method for identifying a gene involved in determining whether or not a neural cell can aid repair on transplantation into a damaged brain, comprises:
(i) isolating cells that are, or are capable of differentiating into, a cell with a neural cell phenotype;
(ii) obtaining the gene expression profile of the cells;
(iii) comparing the expression profile of the cells with that from a control cell line known to be suitable for transplantation; and
(iv) isolating those genes that are the same (or different) from those expressed by the control.
Using this method, it has been possible to identify a number of genes that are expressed by repairing cell lines but not non-repairing cell lines (and vice versa).
According to a third aspect, a method for selecting a cell suitable for transplantation into a damaged brain, comprises determining the presence of any of the gene sequences identified herein as SEQ ID NOS. 1 to 5.
SEQ ID NOS. 1-7 are polynucleotide sequences useful according to the subject invention.